Low energy cured composite repair system based on imidazole-blocked naphthyl-diisocyanates

Abstract

A fiber reinforced resin matrix composite material repair system is provided, which critically employs a resin comprising a catalyst of the formula I: ##STR1## with a multifunctional epoxy resin, the resin system being sealed in a water-proofed environment prior to being coated onto a fiber reinforcement. The coated fiber reinforcement is applied over the damaged area, the damaged portion having been removed, and the surrounding surface smoothed. An adhesive is applied to the remaining surface, prior to application of the patch. The resulting patch, which may further include thermoplastic toughening agents and an enhancer, can be directly cured at temperatures below 212° F. to give physical properties similar to the original material.

What is claimed is: 
     
       1. A method of making on-site repairs of a structure comprised of oriented fiber/resin matrix composite material, which material has been damaged, said method comprising: a) removing the damaged portion from said structure,   b) smoothing those portions of said structure surrounding said excised damaged portion which exhibit rough edges, and applying an epoxy adhesive thereto,   c) applying a patch of epoxy resin system impregnated fiber material over that portion of said structure previously occupied by said damaged portion and adhering it to said smooth edges, the resin system having a shelf life in excess of one year, and comprising at least one multifunctional epoxy resin and a catalyst of the formula: ##STR4## wherein x, y, and z may be the same or different, and each may be hydrogen, a lower alkyl or aryl of C 1-12 , halo or nitro, in an amount of 5-15 pph,   d) applying pressure to said patch to adhere it to said structure and heating said patch to a temperature not more than the boiling point of water for a time sufficient to cure said resin system.   
     
     
       2. The process of claim 1, wherein said resin system further comprises a thermoplastic toughening agent in an amount of 0.1-25% by weight. 
     
     
       3. The process of claim 2, wherein said resin system further comprises a thermoplastic toughening agent enhancer comprised of a polyester rubber resin, in an amount of 0.5-5%, by weight. 
     
     
       4. The process of claim 1, wherein said patch under pressure is heated directly to a temperature of about 170° F.-200° F., for a period of 2-3 hours.